Flanges, i.e. ribs or rims extending from a pipe, are often used when connecting two pipes together because of the ability to disassemble the pipes when necessary. The flanges may be part of the pipe itself, such as a flanged-end pipe, or may be connected to the end of the pipe via a variety of means. Flanges which connect to the end of the pipe include, for example, screw-on flanges, slip-on flanges, socket-weld flanges, lap-joint flanges, welding neck flanges, and blind flanges. These flanges are illustrated in, for example, Perry's Chemical Engineers' Handbook, Sixth Edition, McGraw Hill Book Company, 1984, p. 6-46, which is incorporated by reference. The flanges often have a gasket between them which, unfortunately, may be flammable and could result in a leak in the event of a fire. The flanges are bolted together. Typical gaskets and bolting means are illustrated in, for example, Perry's Chemical Engineers' Handbook, Sixth Edition, McGraw Hill Book Company, 1984, pp. 6-46 through 6-50, which is incorporated by reference.
Often pipes connected by flanges are to be utilized in applications which require that the pipes and flanges be subjected to an external environment which is corrosive and/or subject to fire. An example of such is offshore drilling and production platforms, or other marine structures, wherein the pipes and flanges are subjected to the corrosive salt water of the ocean and possible fires due to the flammability of the produced oil and gas. While methods and apparatuses have been developed which are used to protect the pipes from the corrosive environment and fire, the methods and apparatuses are generally not effective when used for a flange. Methods and apparatuses to protect pipes include those of U.S. Pat. Nos. 5,087,154; 5,591,265; and 5,226,751.
U.S. Pat. No. 5,087,154 relates to a protective coating which has two uninterrupted and encapsulating and superposed layers of a marine resistant epoxy composition and a thin layer of reinforcing composition between the layers. Correspondingly, U.S. Pat. No. 5,591,265 relates to a protective coating which has a formwork around a tube to be protected, an annular space between the tube and formwork, a means to apply a curable resin to the annular space, a seal means, and a support ring secured to the tube. Unfortunately, the protective coatings taught in these two patents are adapted especially for pipes and if used on a flange would be difficult to secure around the flange and completely encompass the flange due to the flange's shape. Therefore, the flange would not be fully protected in many instances. In addition, the protective coatings of the two patents are not adapted for removal and replacement. Therefore, if inspection, repair, or replacement of the flange becomes necessary after the protective coating is applied, then the protective coating would have to be removed at considerable cost or the entire flange would have to be cut from the pipe.
U.S. Pat. No. 5,226,751 relates to a process for creating a controlled environment about a submerged pile by placing a jacket around the pile and then injecting air and a preheated gas into the jacket to dry the pile. After the pile is dry, the jacket is filled with a firm resilient non-corroding compound such as an expanding closed cell foam formed from liquid chemicals or epoxy resins. Unfortunately, if this process was employed on piling containing a flange, then the jacket would leave a very large annular space around the pipe where the flange is located. This would necessitate using a large amount of the very expensive filler. In addition, if the flange needed to be inspected, then it would require removing the protective covering which covers the pipe, as well as, the flange.
Another method which is often employed to protect flanges is that of cathodic protection. Cathodic protection, as described in, for example, Encyclopedia of Science and Technology, Vol. 4, pp. 440-445, McGraw-Hill, 1992, generally involves applying a cathodic potential, or current, to the flange. The cathodic potential prevents the flange from undergoing an anodic reaction, M.fwdarw.M.sup.n+ +ne.sup.-, which causes corrosion. This is often achieved by applying a cathodic current through an auxiliary electrode (impressed current) or by coupling the metal to be protected with a metal having a more negative open circuit potential (sacrificial anode). Unfortunately, such cathodic protection is often uneconomical. Additionally, cathodic protection is not particularly effective for flanges which are subject to both wet and dry conditions, such as flanges in a splash zone of an offshore drilling and production platforms, or other marine structures.
It would be desirable if an alternate method and apparatus suitable for protecting flanges from corrosion and/or fire could be developed. It would be beneficial if such an apparatus was adapted to be removed so that the flange could be inspected and repaired when necessary. It would be advantageous if the apparatus could be reused after removal from the flange. It would further be desirable if such flange protection could be accomplished in an environment which is subject to both wet and dry conditions, impact, abrasion, or ultraviolet light.